Reversible work of the formation of a layer of a new phase on a spherical charged conductor within a uniform multicomponent macroscopic mother phase


A thermodynamically consistent formalism is applied to calculate the reversible work needed to form a small layer of a new phase (embryo) around a charged insoluble conducting sphere within a uniform macroscopic mother phase. To treat the embryos of arbitrary size which are not the critical nuclei (i.e., which are not fragments that are in unstable equilibrium with the mother phase), a constraint in the form of an external field is introduced. When a critical nucleus is of primary interest, the specification of this constraint is not required. The results that are obtained for a critical cluster do not depend on which path approaches a critical state. However, the properties of noncritical clusters depend on the external constraining field and this effect is discussed in detail. The obtained new expression for the work of embryo formation differs from the one commonly used in the nucleation literature. The conditions of its extrema yield the correct conditions of equilibrium between the critical nucleus and the mother phase. Expressions are derived that are suitable for practical calculations of the size and composition of a critical nucleus. (C) 2003 American Institute of Physics.